This invention is directed to ion injectors and more specifically to injectors for generating negative ions.
A number of injectors are used for producing negative ions. Typically such injectors include a source of positive ions that produces a positive ion beam, separate electromagnets for analyzing and focusing the beam, and a charge conversion apparatus that transfers electrons to the positive ions thereby to convert the positive ions to negative ions. More particularly, such charge conversion apparatus vaporizes some substance, such as lithium, to produce a vapor through which the positive ion beam must pass. As the positive ion beam passes through the vapor, electrons transfer to the ions thereby converting them to negative ions to produce a negative ion beam.
Obviously if the charge conversion apparatus produces a vapor, there will a partial pressure. Given the typically low energy of ion beams in such injectors, it is not practical to isolate such an area from the vacuum area by vacuum windows. The inclusion of such windows would reduce the energy of the beam and further would tend to destroy its optical properties. Without such isolation, however, the vapor must be contained and recovered efficiently in order to minimize its deposit on other portions of the apparatus. If such efficient containment and recovery is not possible, then the vapor reaches the vacuum portions of the system. Moreover, the vapor is lost, so it is constantly necessary to interrupt operations and replenish the material, such as lithium in liquid state, from which the vapor is produced. In the past various recovery schemes have been proposed and used, but they have not been particularly efficient.
Therefore, it is an object of this invention to provide an improved injector of negative ions.
Another object of this invention is to provide an improved vapor canal for converting positive ions to negative ions.
Still another object of this invention is to provide an improved vapor canal that is constructed to maximize vapor containment and recovery.